Refractive index of air, μair = 1;
Given;
Refractive index of water w.r.t air, aμw = \(\frac43\)
Refractive index of glass w.r.t air, aμg = \(\frac32\)
Refractive index of water w.r.t glass = gμw = \(\frac{^aμ_w}{^aμ_g{^c}}=\frac{\frac43}{\frac32}\)
⇒ gμw = \(\frac{4\times2}{3\times3}=\frac89\)
∴ Refractive index of water w.r.t glass is \(\frac89\)
Also;
Refractive index of water w.r.t glass. = \(\frac{1}{Refractive\,index\,of\,glass\,w.r.t\,water.}\)
⇒ Refractive index of glass w.r.t water = \(\frac{1}{Refractive\,index\,of\,water\,w.r.t\,glass}\)
∴ Refractive index of glass w.r.t water = \(\frac{1}{\frac89}=\frac98\)
Refractive index of glass w.r.t water =\(\frac98\)